1 files changed, 99 insertions, 0 deletions
diff --git a/framework/src/onos/core/api/src/main/java/org/onosproject/event/ListenerRegistry.java b/framework/src/onos/core/api/src/main/java/org/onosproject/event/ListenerRegistry.java
new file mode 100644
index 00000000..ef02af06
--- /dev/null
+++ b/framework/src/onos/core/api/src/main/java/org/onosproject/event/ListenerRegistry.java
@@ -0,0 +1,99 @@
+/*
+ * Copyright 2014 Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.onosproject.event;
+
+import org.slf4j.Logger;
+
+import java.util.Set;
+import java.util.concurrent.CopyOnWriteArraySet;
+
+import static com.google.common.base.Preconditions.checkNotNull;
+import static org.slf4j.LoggerFactory.getLogger;
+
+/**
+ * Base implementation of an event sink and a registry capable of tracking
+ * listeners and dispatching events to them as part of event sink processing.
+ */
+public class ListenerRegistry<E extends Event, L extends EventListener<E>>
+        implements ListenerService<E, L>, EventSink<E> {
+
+    private static final long LIMIT = 1_800; // ms
+
+    private final Logger log = getLogger(getClass());
+
+    private long lastStart;
+    private L lastListener;
+
+    /**
+     * Set of listeners that have registered.
+     */
+    protected final Set<L> listeners = new CopyOnWriteArraySet<>();
+
+    @Override
+    public void addListener(L listener) {
+        checkNotNull(listener, "Listener cannot be null");
+        listeners.add(listener);
+    }
+
+    @Override
+    public void removeListener(L listener) {
+        checkNotNull(listener, "Listener cannot be null");
+        if (!listeners.remove(listener)) {
+            log.warn("Listener {} not registered", listener);
+        }
+    }
+
+    @Override
+    public void process(E event) {
+        for (L listener : listeners) {
+            try {
+                lastListener = listener;
+                lastStart = System.currentTimeMillis();
+                if (listener.isRelevant(event)) {
+                    listener.event(event);
+                }
+                lastStart = 0;
+            } catch (Exception error) {
+                reportProblem(event, error);
+            }
+        }
+    }
+
+    @Override
+    public void onProcessLimit() {
+        if (lastStart > 0) {
+            long duration = System.currentTimeMillis() - lastStart;
+            if (duration > LIMIT) {
+                log.error("Listener {} exceeded execution time limit: {} ms; ejected",
+                          lastListener.getClass().getName(),
+                          duration);
+                removeListener(lastListener);
+            }
+            lastStart = 0;
+        }
+    }
+
+    /**
+     * Reports a problem encountered while processing an event.
+     *
+     * @param event event being processed
+     * @param error error encountered while processing
+     */
+    protected void reportProblem(E event, Throwable error) {
+        log.warn("Exception encountered while processing event " + event, error);
+    }
+
+}